Failure after short time

[Dicko4]

my SLY500K2 on sliding gate has worked well for some time. Suddenly all openers fail. Reset and they all work but only for a short time. They will all be ok after a reset and then fail again. The key switch is the same. Power is OK. I am flummoxed can you help please

[Dicko4]

I noticed that the photocells were not illuminated when gate failed.
When they came on again bingo gate worked.
I concluded poor photo cell connection maybe due to rain.
However next thing failure when photocell illuminated.
I then turned power off and on and operation returned
What can I conclude?
My thought is bad connection what say you and where to look